1. Field of the Invention
The present invention generally relates to touch panels, and more particularly to a touch panel with a ground ring design that can reduce the area of the rim of the touch panel.
2. Description of the Related Art
Touch displays combining sensor and display technologies to form input/output modules such as touch panels are commonly used in electronic appliances, such has portable and handheld electronic devices.
The capacitive type touch panel is the most commonly used touch panel, using capacitive coupling effects to detect touch location. When conductive pointers such as a user's finger(s) approach or touch the surface of the capacitive touch panel, capacitance(s) corresponding to the touch location(s) will be altered and thus the touch location(s) can be detected.
FIGS. 1A and 1B respectively show a cross-sectional view and a top view of a touch panel. The structure of FIG. 1A exhibits a glass substrate 2, a black matrix 8 on the peripheral area of the lower surface of the glass substrate 2 and a touch sensor layer 4 disposed under the glass substrate 2 and the black matrix 8. The touch sensor layer 4 includes an electrode layer to detect touch location. A trace 11, a grounding ring 12, a first overcoat layer 15 and bridges 17 exist on the lower surface of the touch sensor layer 4. A second overcoat layer 6 is configured to cover the touch sensor layer 4, the trace 11, the grounding ring 12 and the first overcoat layer 15. The trace 11 and the grounding ring 12 are located beneath the black matrix 8.
The layout of FIG. 1B corresponds to an electrostatic discharge protection design utilizing the grounding ring 12, surrounding electrodes 14 and 16, and conductive lines 18 on the touch panel. FIG. 1B also shows the bridges 17 connecting adjacent pairs of electrodes 16.
However, since the size of touch panel is limited, in order to increase the touch control area and the display area on the touch panel, the width of the black matrix 8 or the width of the rim of the touch panel must be reduced as far as possible, to obtain a narrower rim. Thus, while the size of touch panel maintains unchanged, the outline dimension can be reduced. Nevertheless, since the trace 11 and the grounding ring 12 are located just beneath the black matrix 8, attempts at decreasing the width of the black matrix 8 are restricted.
Therefore, there is a need to propose an innovative touch panel to improve the shortcomings of the traditional touch panel.